'Supernatural' Surprises Comic-Con With Live Performance by Kansas

Check out video of the rock group's performance of "Carry on Wayward Son," the unofficial theme song of The CW's longest-running series.

Supernatural's San Diego Comic-Con panel turned into a rock concert on Sunday morning.

The band Kansas surprised the thousands of fans gathered in Hall H with a performance of the show's unofficial theme song, "Carry on Wayward Son." The tune was first used back on the season one finale during a montage and has been used for every season finale since then. It has been fully embraced by the Supernatural fanbase as the song of the series, and was even reprised during the show's 200th episode with a slowed-down version as a love letter to the fans.

Series stars Jensen Ackles and Jared Padalecki wanted to watch the performance and tried on masks to hide their identity so they could rock out in the crowd incognito, but nothing could sufficiently hide them, so they had to watch from the back corner of the giant venue. Only one dancing fan noticed them and freaked out after asking them to take a photo of her, not realizing at first who she was asking.

The Hollywood Reporter was on the scene for the surprise performance that kicked off the panel. Check out the full video of the amazing moment, below.

During the panel, when asked about Castiel's (Misha Collins) death in the season 12 finale, executive producer Bob Singer said, "You have to go where the story takes you. Perhaps Castiel's time had come. Frankly, Misha had become a bit of a prima donna, wanted to be No. 1 on the call sheet..."

Of course, that's when Collins came onstage, crashing the panel and surprising the audience with a much smaller chair than the rest of his castmates. Ackles then jokingly asked him how it felt to not be on the show anymore. But he promised fans, "I'm not going away." And Singer confirmed that Castiel will be back, but wouldn't elaborate on how.

The series also announced casting for the upcoming potential new spinoff series Wayward Sisters. Set in the world of Supernatural, the pilot will air as an episode this season centered on Sheriff Jody Mills (Kim Rhodes) and a group of troubled young women — all orphaned by supernatural tragedy — as they emerge as a formidable force against the supernatural, under Mills’ training and protection.

Lending Jody a hand will be series fan-favorite Sheriff Donna Hanscum (Briana Buckmaster), a relative novice to the hunter’s life, but a close friend whom Jody can confide in. The group of young girls includes Claire Novak (Kathryn Newton), Alex Jones (Katherine Ramdeen) and new character Patience Turner (Clark Backo of Designated Survivor), a high school overachiever whose life is turned upside down when she discovers she’s a powerful psychic, a gift she inherited from her estranged grandmother, season one's Missouri Moseley (Loretta Devine). Hunted by dark forces for her power, Patience finds refuge with Jody and her wayward family. And Missouri Moseley will be back in an episode this season as well.

Check out the season 12 highlight reel debuted during the panel, below.

Season 13 of Supernatural premieres Thursday, Oct. 12, at 8 p.m. ET/PT on The CW.